1. Field of the Invention
This invention is directed to X-ray apparatus, and more particularly, to improvement in an X-ray table tiltable about a pivot. The table has an imaging device (a spot filmer or the like) mounted on a tower. The tower is in turn movably attached to the table. The table includes a mechanism for counterbalancing the mass of the tower when the table is tilted.
2. Description of the Prior Art
In X-ray examination apparatus, it is known to provide radiological systems including a so-called 90-90 X-ray table in which a table body and its associated top are tiltable on a pedestal about an axis transverse to the table length. Such tables are tiltable in either direction 90.degree. from a position in which the table top is horizontal. Thus, the body of the table may be moved clockwise or counterclockwise from the horizontal until its top is vertical, or to any position between the vertical positions. Drive structure, including a reversible electric motor and circuitry to control it, is provided for effecting the desired tilting motion. One such table is that described and claimed in the referenced Schiring, et al., U.S. Pat. No. 2,872,584.
Other tables with lesser degrees of tiltability are also known. Some tables, for example, have a body which is tiltable in one direction from a top-horizontal position to a vertical position, and tiltable in the other direction to a so-called "Trendelenburg" position where the angle of the table is approximately 15.degree. from the horizontal.
In most tiltable tables, a guide track is provided parallelling longitudinally the table top. A movable column or tower is slidably mounted on the guide track for movement on a path of travel which is longitudinal with respect to the table top. The column is also mounted for reciprocable rectilinear movement along a guide path transverse to the table top and normal to the column travel along the guide track.
The column supports an X-ray tube which is positioned beneath the table top and within the table body. One or more image producing X-ray responsive devices such as a spot filmer or an image intensification device are supported by a carriage, which is reciprocally mounted on the column for travel along a rectilinear path perpendicular to the plane of the table top.
These three paths of travel permit the carriage to be moved to any selected position over the table top and to any selected distance from the top within the limits of the respective paths of travel.
Since the motion of the column along the guide track has a vertical component when the table top is in a nonhorizontal position, at least one counterweight is used to counterbalance the column. The counterweight is desirable in preventing the heavy tower from tending to slide toward the lowered end of the X-ray table when tilted.
It is known to provide mechanical linkage between the tower and the counterweight to effect automatic counterbalancing of the weight of the tower as the tower is moved along the guide track, so that the table is always in a substantially balanced condition about its pivot on its pedestal.
According to one system, the counterweight is slidably mounted for longitudinal movement parallel to the guide track within the body of the table along a counterweight track. The counterweight and the tower (each weighing about 600 pounds) are connected together by two main or primary connectors made of suitable woven wire cable having an outside diameter of about 3/16 inch.
The cable portions are connected between the counterweight and the tower by way of their engagement with pulleys located at and within opposite ends of the table body. One portion of cable is connected to one side of the counterweight, and extends outwardly around the pulley at one end of the table, and then inwardly to a point at which it is attached to the tower. The other portion of cable extends from the opposite side of the counterweight toward the other end of the table, around the pulley located there, and back toward an attachment to the tower.
With this arrangement, motion of the tower in one direction causes an equal amount of motion of the counterweight in the opposite direction. The lengths of the two portions of cable, and the locations of the pulleys, are selected such that the counterweight is directly aligned with the table's pivot axis when the column is also so aligned, and so that the counterweight moves toward one end of the table when the tower is moved toward the opposite end.
An object of this invention is to provide apparatus and method for detecting and indicating the occurrence of excessive strain or failure in a main support of the X-ray table system.